<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <style>
      html,
      body {
        margin: 0;
        padding: 0;
        width: 100%;
        height: 100%;
      }
    </style>
    <script>
      function gradientColor(startColor, endColor, step) {
        var startRGB = this.colorRgb(startColor); //转换为rgb数组模式
        var startR = startRGB[0];
        var startG = startRGB[1];
        var startB = startRGB[2];
        var endRGB = this.colorRgb(endColor);
        var endR = endRGB[0];
        var endG = endRGB[1];
        var endB = endRGB[2];
        var sR = (endR - startR) / step; //总差值
        var sG = (endG - startG) / step;
        var sB = (endB - startB) / step;
        var colorArr = [];
        for (var i = 0; i < step; i++) {
          //计算每一步的hex值
          var hex = this.colorHex(
            'rgb(' + parseInt(sR * i + startR) + ',' + parseInt(sG * i + startG) + ',' + parseInt(sB * i + startB) + ')'
          );
          colorArr.push(hex);
        }
        return colorArr;
      }
      // 将hex表示方式转换为rgb表示方式(这里返回rgb数组模式)
      gradientColor.prototype.colorRgb = function (sColor) {
        var reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
        var sColor = sColor.toLowerCase();
        if (sColor && reg.test(sColor)) {
          if (sColor.length === 4) {
            var sColorNew = '#';
            for (var i = 1; i < 4; i += 1) {
              sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1));
            }
            sColor = sColorNew;
          }
          //处理六位的颜色值
          var sColorChange = [];
          for (var i = 1; i < 7; i += 2) {
            sColorChange.push(parseInt('0x' + sColor.slice(i, i + 2)));
          }
          return sColorChange;
        } else {
          return sColor;
        }
      };
      // 将rgb表示方式转换为hex表示方式
      gradientColor.prototype.colorHex = function (rgb) {
        var _this = rgb;
        var reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
        if (/^(rgb|RGB)/.test(_this)) {
          var aColor = _this.replace(/(?:(|)|rgb|RGB)*/g, '').split(',');
          var strHex = '#';
          for (var i = 0; i < aColor.length; i++) {
            var hex = Number(aColor[i]).toString(16);
            hex = hex < 10 ? 0 + '' + hex : hex; // 保证每个rgb的值为2位
            if (hex === '0') {
              hex += hex;
            }
            strHex += hex;
          }
          if (strHex.length !== 7) {
            strHex = _this;
          }
          return strHex;
        } else if (reg.test(_this)) {
          var aNum = _this.replace(/#/, '').split('');
          if (aNum.length === 6) {
            return _this;
          } else if (aNum.length === 3) {
            var numHex = '#';
            for (var i = 0; i < aNum.length; i += 1) {
              numHex += aNum[i] + aNum[i];
            }
            return numHex;
          }
        } else {
          return _this;
        }
      };

      let colors = new gradientColor('#013548', '#554851', 10);

      console.log('colors ', colors);
    </script>
  </body>
</html>
